[PATCH 16/22] xen-blkfront: Make use of the new sg_map helper function

[Logan Gunthorpe <logang-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>]

Straightforward conversion to the new helper, except due to
the lack of error path, we have to warn if unmapable memory
is ever present in the sgl.

Signed-off-by: Logan Gunthorpe <logang-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
---
 drivers/block/xen-blkfront.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 5067a0a..7dcf41d 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -807,8 +807,19 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 		BUG_ON(sg->offset + sg->length > PAGE_SIZE);
 
 		if (setup.need_copy) {
-			setup.bvec_off = sg->offset;
-			setup.bvec_data = kmap_atomic(sg_page(sg));
+			setup.bvec_off = 0;
+			setup.bvec_data = sg_map(sg, SG_KMAP_ATOMIC);
+			if (IS_ERR(setup.bvec_data)) {
+				/*
+				 * This should really never happen unless
+				 * the code is changed to use memory that is
+				 * not mappable in the sg. Seeing there is a
+				 * questionable error path out of here,
+				 * we WARN.
+				 */
+				WARN(1, "Non-mappable memory used in sg!");
+				return 1;
+			}
 		}
 
 		gnttab_foreach_grant_in_range(sg_page(sg),
@@ -818,7 +829,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
 					      &setup);
 
 		if (setup.need_copy)
-			kunmap_atomic(setup.bvec_data);
+			sg_unmap(sg, setup.bvec_data, SG_KMAP_ATOMIC);
 	}
 	if (setup.segments)
 		kunmap_atomic(setup.segments);
@@ -1468,8 +1479,18 @@ static bool blkif_completion(unsigned long *id,
 		for_each_sg(s->sg, sg, num_sg, i) {
 			BUG_ON(sg->offset + sg->length > PAGE_SIZE);
 
-			data.bvec_offset = sg->offset;
-			data.bvec_data = kmap_atomic(sg_page(sg));
+			data.bvec_offset = 0;
+			data.bvec_data = sg_map(sg, SG_KMAP_ATOMIC);
+			if (IS_ERR(data.bvec_data)) {
+				/*
+				 * This should really never happen unless
+				 * the code is changed to use memory that is
+				 * not mappable in the sg. Seeing there is no
+				 * clear error path, we WARN.
+				 */
+				WARN(1, "Non-mappable memory used in sg!");
+				return 1;
+			}
 
 			gnttab_foreach_grant_in_range(sg_page(sg),
 						      sg->offset,
@@ -1477,7 +1498,7 @@ static bool blkif_completion(unsigned long *id,
 						      blkif_copy_from_grant,
 						      &data);
 
-			kunmap_atomic(data.bvec_data);
+			sg_unmap(sg, data.bvec_data, SG_KMAP_ATOMIC);
 		}
 	}
 	/* Add the persistent grant into the list of free grants */
-- 
2.1.4